Re: PostgreSQL, and ODBC statement handles

Hi Hiroshi,
In /etc/odbcinst.ini, I set “Threading = 0”. I can see multiple server processes in transaction in the backend server. The contention appears to be only for access to the statement handle, not actual database access. For example, when I replaced looping over SQLFetch(stmt) with a single SQLFetchScroll(stmt, SQL_FETCH_NEXT, 0), I got better results. Same with reducing the frequency of calls to SQLBindCol()
Thanks,
Reza

On 5/3/17, 10:38 PM, "Inoue, Hiroshi" <h-inoue(at)dream(dot)email(dot)ne(dot)jp<mailto:h-inoue(at)dream(dot)email(dot)ne(dot)jp>> wrote:

Hi Reza,

How are you setting 'Threading' in odbcinst.ini?

regards,
Hiroshi
On 2017/05/04 14:08, Reza Taheri wrote:
I am running a benchmark (TPCx-V) with a single process on the client system handing all the load. Each connection to the server is in a separate thread with its own connection to PGSQL, and its own connection handle and statement handle. I am facing a contention problem with ODBC on the client side. strace and perf top show we are serializing over what appears to be accesses to the ODBC statement handlepgsq. Contention goes away if I use multiple processes instead of multiple threads within a process.

I suppose I don’t understand the concept of “handles” well, but I am surprised that all the threads get the same connection handle number and the same statement handle number. Does that mean some data structure is shared between the different threads? Is there a way to force different statement handles (or handle numbers???) for different threads within one process? I have asked this question on the ODBC mailing list, and they suggested it could be something in the postgresql driver. I can provide detailed performance data, but maybe someone can help me figure out what might be a very basic configuration or parameter setting problem. I am running the following RPMs on RHEL 7.1:
postgresql93-9.3.5-2PGDG.rhel7.x86_64
postgresql93-odbc-09.03.0300-1PGDG.rhel7.x86_64
unixODBC-2.3.1-10.el7.x86_64

Thanks,
Reza